1. Field of the Invention
The invention relates to analog-to-digital converters, and more particularly, to adjusting a sampling condition of an analog-to-digital converter.
2. Description of the Prior Art
Choosing a sampling condition for an analog to digital converter (ADC) is a very important operation and generally speaking includes, but is not limited to, adjusting the phase and/or the frequency of a sampling clock for the ADC. There are a wide variety of applications that require methods for adjusting the sampling condition of an ADC. For example, in a liquid crystal display (LCD), a received analog input signal is normally coupled to an ADC to convert the received analog input signal into a digital sampled signal. However, reductions in sampling quality will likely result due to a non-optimal ADC sampling condition. Because of this, LCDs normally also include an automatic phase setting function and/or an automatic clock setting function to automatically adjust the sampling condition of the ADC.
Taking the automatic phase setting function as an example, the sampling condition for the ADC is formed according to different sampling phases. In this way, the ADC converts an analog signal into a digital signal utilizing different sampling phases, and calculates a characteristic value for the digital signals obtained for each of the different sampling phases according to a particular algorithm. For example, a sum of differences (SOD) value can be calculated for the digital signal according to a particular algorithm. By means of comparing the calculated characteristic values, a preferred sampling phase can be chosen. Afterwards the ADC performs sampling operations according to the preferred sampling phase.
However, the sampling condition adjusting method according to the SOD value does not necessarily provide adequate information to choose an optimal sampling condition. For example, if the range of change of the input signal is very small for most of the time that each SOD value is being calculated, the difference between different SOD values obtained for the different sampling conditions will not be significant, and this results in difficulty choosing which is the optimal sampling condition.